The invention relates to a device for reading information stored on an information disc, for writing information on an information disc, or for performing both functions. Such a device is known, for example, from the publication EP 0892403.
The term information disc here is understood to mean a plate-shaped data carrier, in particular a CD, CD-ROM, and DVD.
In the known device, a mechanical stop is provided against which the information disc is abutted during the loading process for the purpose of positioning the information disc above the turntable of a playback unit.
It is an object of the invention to provide a device of the kind mentioned in the opening paragraph, which renders possible an accurate positioning of an information disc on the turntable of a playback unit.
According to the invention, this object is achieved in that the device comprises at least one position switch for recognizing the position of the information disc, in that the position switch comprises at least two detection elements for scanning two mutually distanced reference points, and in that said reference points are arranged on the circumference of a circle whose center corresponds to the center of the information disc in a reference position.
It is possible that such a position sensor to detect the position of the information disc exactly in two dimensions and to position the information disc exactly in a desired location in two dimensions. In particular, the position sensor is suitable for an exact positioning of the information disc above the turntable of a playback unit. The reference position in this case is the center of the turntable.
The advantageous embodiment of the invention as defined in claim 2 is particularly inexpensive and simple to realize.
The optical solution as defined in claim 3 can be integrated into compact devices in a particularly space-saving manner. The optical contact pairs each form a photoelectric barrier. The photoelectric barrier is interrupted the moment the disc edge of the information disc reaches the relevant reference point.
The advantageous embodiment of the invention as defined in claim 4 has the advantage that the positions of the two reference rims with respect to one another can be manufactured with very narrow tolerance in stamping technology. The advantage of this construction is that the switching point can be maintained very accurately without adjustment.
The embodiment of the invention as defined in claim 5 has the advantage that the contacts still move relative to one another after closing. This achieves a self-cleaning effect of the contacts.
At the same time, the reference rims for the edge of the information disc must be kept fixedly positioned with respect to the center of the turntable. To achieve this, the reference rims are rigidly fastened in the housing of the switch, whereas the contacts are fastened to resilient spring arms.
The embodiment of the invention as defined in claim 6 has the advantage that the connection of the two contacts inside the switch reduces the expenditure for contacting by means of cables or foils.
It is advantageous for reasons of space in devices as defined in claim 7, which comprise a stacking function in addition to the playback function (changer devices), when the transport of the information discs to the turntable can take place in two loading directions. A first loading direction is, for example, the transport of the information disc from an ejection position outside the device onto the turntable, while a second loading direction is, for example, the transport of the information disc from the stacking unit to above the turntable. The exact position of the information disc above the turntable can be detected two-dimensionally by means of the position sensor according to the invention so as to lay the information disc on the turntable subsequently such that the centering pin of the turntable enters the central hole of the information disc.